Fungi are microscopic, spore-bearing organisms that lack chlorophyll and therefore derive nourishment from dead or living organic matter [Alexopoulos, C. J., et al., Introductory Mycology (1979), Chapter 1]. Because they share characteristics of both plants and animals, they are classified separately in the Kingdom Myceteae. Within this Kingdom, there are the "filamentous fungi," so named because their vegetative bodies consist of small filaments referred to as "hyphae." Typically, the hyphae grow in a branching fashion, spreading over or within the substrate used as the source of nourishment, thereby forming a network of hyphae called "mycelium." In the life cycle of most filamentous fungi, the mycelium gives rise to either asexual or sexual reproductive bodies bearing spores. The spore is functionally comparable to the seed of higher plants, being important in the dispersal and survival of the fungus in nature. Under suitable environmental conditions, the spore germinates to form another generation of hyphae and so completing the life cycle of the fungus.
Perhaps filamentous fungi are best known for their edible, fleshy, sporebearing, reproductive structures called "mushrooms." Mushrooms have been grown commercially for many years. Throughout these years, commercial production of cultivated mushrooms has increased dramatically. In 1939, worldwide production of Agaricus bisporus (also referred to as Agaricus brunnescens), the most popular of the edible cultivated mushrooms, was 46,000 tons. By 1982, such production was in excess of 850,000 tons [Flegg, P. B. and Wood, D. A., The Biology and Technology of the Cultivated Mushroom, Chapter 1, p. 7 (1985)].
The common edible mushroom (e.g., A. bisporus) has both vegetative and reproductive ("fruiting") forms. The form most familiar to consumers is the fruiting form (i.e., mushroom), which has a stalk and an umbrella shaped cap. The life cycle of this mushroom fungus begins with the germination of a spore, which produces hyphae. A collection of hyphae compact together and form the mycelium. The mycelium then grows and invades the environment as networks. Small masses at the periphery of the network of mycelium enlarge and differentiate to form immature mushrooms called "buttons." The buttons rapidly enlarge and burst through the soil and become mature mushrooms. Mushrooms are produced from mycelium in cycles referred to as "breaks" or "flushes." A single population of mycelium may produce multiple breaks. The mushrooms then produce spores which germinate and produce further mycelium.
Methods of commercial mushroom cultivation are well known and generally involve inoculating beds or trays of compost with mushroom spawn. Such compost is rich in nutrients and capable of supporting the mushroom fruiting stage. As used herein, the term "spawn" refers to a nutrient substrate, typically rye or millet, colonized by mycelium. In the process referred to as "spawning," the spawn is mixed with compost to promote growth of the mycelium throughout the compost. The compost is usually comprised of straw-bedded horse manure or other combinations of fibrous plant material. Several weeks after spawn dissemination, when the compost has been sufficiently colonized by the fungus, the compost is covered with a thin layer of "casing soil" (e.g., peat, soil). This process is called "casing." Within weeks of casing, mushrooms develop and are harvested in breaks. U.S. Pat. No. 4,803,800 is related to same.
Owing to its stimulatory effect on the yield of mushrooms, the addition of protein-rich, lipid-rich supplements (generally soybean meal) to the compost has become a widespread practice in the commercial cultivation of the button mushroom A. bisporus. Typically, supplements are added at the time when the compost is inoculated with the mushroom fungus (SASing, supplementation of spawning). Supplements may also be mixed with the compost at casing (SACing, supplementation at casing). In yet another variation on the time of supplementing, supplements can be added during the mushroom production cycle [Schisler, L. C. 1990. Applied Agricultural Research, 5:44-47].
A salient feature of commercial supplements is that the availability of nutrients is delayed until the mushroom fungus has thoroughly invaded the compost, thereby minimizing early utilization by competitive microorganisms within the compost. The state-of-the-art mechanism of delayed-release involves formaldehyde-denaturation of the protein (Spawn Mate Co.) and encasing the protein in a water-repellent film containing the fungicide Mertect (Thiabendazole) (Campbell Soup Co.). [These techniques are disclosed in U.S. Pat. Nos. 3,942,969; 4,370,159; 4,534,781; and 4,617,047]. However, because these materials contain chemical pesticides, their future in the mushroom industry is tenuous. Formaldehyde has been restricted by the Environmental Protection Agency and California now requires the routine monitoring of workers handling Spawn Mate for exposure to formaldehyde. Campbell Soup's supplement was banned in Canada, although its use is now permitted. Considering the emerging trend towards the reduced usage of chemicals in agriculture, there is an urgent need to develop an environmentally-safe, delayed-release supplement for mushrooms. The present invention overcomes the above-described disadvantages inherent with various compositions and methods of the art. The invention presents compositions, methods for their preparation and use, which permit safe, economical, and convenient application in the commercial production of mushrooms.